It has long been recognized that aircraft and other vehicles operate most efficiently when their weight is minimized. A major contributor to the weight of modern vehicles is the load of communication equipment, including antennas, transmitters, receivers, controllers, input devices such as microphones and cameras, output devices such as monitors and headphones, and transmission lines interconnecting the various elements of the communications system.
In order to reduce weight associated with the communication systems of vehicles, it is common to use full duplex operation of signal paths, so that the transmitted and received signals travel, in opposite directions, over the same transmission lines, thereby saving a substantial portion of the weight associated with transmission paths for the other direction of transmission. A major problem with use of a full-duplex transceiver with an associated antenna is the large dynamic range necessary to isolate the high-level transmitted signal from the low-level received signal. In a transmission path, the presence of unavoidable reflections due to variations in the characteristics of the signal path converts signals flowing in a particular direction into reflected signals which flow in a retrograde direction. The problem of reflections is particularly severe in optical fiber transmission paths.
Improved communication systems are desired.